Furnace-tube



F. J. METZGER.

FURNACE TUBE.

APPLICATION FILED FEB. e, 1920.

UNITED STATES PATENT FLOYD J. METZGER, OF NEW YORK N. Y., -ASSIG-NOIIR. ING, CORPORATION OI NEW;YORK

1 OFFICE.

Am 'annoc'rron comm,

rurmncn ronn To all whom it may concern:

Be it known that I FLOYD METZGER, a citizen of the United tates, residing at New York, in the county of New York, State of- New York, haveinvented certain new and useful Improvements in F urnace-Tubes; and I do hereby declare the following to be .a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to furnace tubes employed in the production of alkali metal cyanid by heating mixtures of alkali metal compounds and carbon, with or without vention will be apparent as itis better under stood by reference to the following specification and to the accompanying drawing, in which,

Figure 1 is a sectional tube illustrating which rapidly tofore used;

Fig. 2 is a longitudinal section through the improved furnace tube;

Fig.v 3 is a, transverse section through the structure illustrated in Fig. 2;

Fig. 4.- isa longitudinal section illustrating a slightly different form of. my invention; and

Fig. 5 is a transverse sectionthrough the structure illustrated in Fig. 4.

In the ractice of the method of producing cyanid by the fixation of nitrogen as described, for example, in Patent N 0. 1,322,195 granted November 18, 1919, iron and steel ;ubes were rapidly consumed by oxidation ind it was'necessary to provide a furnace ube which resisted he heating gases. Nichrome tubes were .dopted for this purpose and successfully net the problem first encountered. These ubes are, however, cast and frequently conview of a furnace the disintegrating influence destroys the. furnace as "here Specification of Letters Patent. Application filed February 6,

tube which will successv provid wrought tubes the oxidizing action of.

Patented Aug. 16, 1921. 1820,, Serial No. 356,734.

tain numerous sand'holes and pores which sometimes extend throu h the. wall. chrome is not directly 8. ected by the alkali metal carbonate or oxid which f of the furnace charge, but when the carbonate or oxid makes its way throu h the holes or pores to it combines with the slightly oxidized coating on the tube and forms a blister, which gradually eats its way through the wall and destroys the tube. 'Nichrome tubes of the size employed are ex ensive and such tubes under working con 'tions may have a life extending from a relatively few days to weekssor months depending upon theporosit The life of the tubes is in any event too s ort to warrant commercial practice of the method, the cost of replacement of the tubes being too great a factor in the production cost of cyanid.

have discovered that this however, be readilg met and overcome by mg a lining or the tubes which is not affected by the alkali metal compound. Ironor steel is not affected by the alkali metal carbonate or oxid and, since drawn or may be readily procured which have no sand holes or pores, I prefer to use a lining of iron or steel although other difficulty may,

material may serve the same purpose. When such a lining is provided, the alkali metal compound cannot reach the'outer surface of the nichrome tube and the destructive action referred to is efl'ectually prevented. The iron .or steel oxidizing action of the heating gases by the nichrome and the combination thus provides an ideal furnace tube which has a practically indefinite life and makes the production of cyanid in the manner described entirely practicable and relatively inexpensive.

he iron or. steel lining may be fitted closely within the nichrome tube so that substantially no space exists between the walls of the respective tubes. On the other hand, the walls may be slightly spaced and the space may be filled with any suitable filler which should preferably be a good conduc,- tor of heat. Finely divided iron which closely packs within the space and thus prevents the entrance of any harmful air current may be used advantagleously. It may orms a part lining is protected from the I vantageous .as carbon, inlquantity sufficient to insure reducing conditions between the tube" walls.

-Practical experience has shown that when the tube is practica ly aseflicient as when a sin le tube of nichrome is used.

. ferring to Fig.1 of the drawing,'5 in-- dicates a nichrome tube in which sand holes or pores 6, which are ma ified in the drawing for purpose of illustration, permit passage 'of the alkali metal. compound to the external surface of the tube. Theblister 7 is thus formed and, in continued operation gradually eats its way through the wall 0 the tube as the alkali metal com ound combines with oxid at thebottom o the blister.

The foregoing represents a condition existing in nichrome tubes employed'in carrying out the nitrogen fixation method referred to above. a

In Figs. 2and 3 of'the drawin the im-- proved furnace tube is illustrate as comprising the outer shell 8 of nichrome and the lining 9 of iron or steel closely fittln wlthin the nichrome shell so as to provi e substantially no air space between the walls. The combined tubes are mounted in a suitable furnace structure such' as is illustrated and described for example, in Patent No. 1,322,195. Such' tubes will successfully withstand the destructive action of the furnace gases and of the alkali metal compound indefinitely and consequently replacements of tubes and the consequent expense and 10 of time is substantially eliminated.

Figs. 4 and 5' of the drawing illustrate a slightly different form of the invention in which an outer tube 10 of nichrome and a lining 11 of iron or steel are provided. The

-lining 11 is spaced from the outer tube preferably by a flange 12 at one end and adjusting screws 13 at the other, thus permittin endwise expansion of the tubes indepen ently ofv each other. Between the tubes a filling 14 of finely divided iron or other suitable material is disposed, the material being closely packed, a result which is accomplished without special attention since the tube is mounted in an inclined position. A reduc'in agent such as carbon may ad- %y be mixed with the iron though it is not essential to the successful accomlishment of the desired result. The space tween the outer tube and lining is preferably closed and made air-tight as indicated at 15 by means of asbestos cement or-other suitable material.

As above pointed out, heat is conductedthrough the walls of the duplex tube substantially 'as through the nichrome tube,

formerly used, ,and consequently the method of making cyamd may be carried out efl'ecnace tube is safe tivelly using the novel structure which entire to o the single nichrome tube.

Various changes may be m nace and I desire, therefore, to claim as my invention the arrangement whereby the fu'rarded against oxidation and the destructive action of the alkali metal'compound.

'I' claim:

1. A furnace tube outer shell of oxldation mistant material and a'relativel thin inner nonporous shell of material w ich is not affected by said alkali metal compound.

2. A furnace tube adapted for use in the fixation of nitrogen by heating mixtures of alkali metal compounds and carbon in the presence of nitrogen, which com rises, an outer shell of nichrome and a relatively thin inner shell of ferrous metal.

3. A furnace tube adapted for use in the fixation of nitrogen by heating mixtures of alkali metal compounds and carbon in the presence of nitrogen, which comprises, an outer shell of oxidation resistant material, an inner shell .of material which is not affected by said alkali metal compound, the walls of said shells being spaced, and a heat conducting filler disposed between said walls.

4. A furnace tube adapted for use in the fixation of nitrogen by heating mixtures of' alkali metal compounds and carbon in the presence of nitro n, which comprises, an outer shell of oxidation resistant material, an inner shell of material. which is not affected by said alkali metal compound, the walls of said shells being spaced, and a filler comprisin finely divided iron disposed between sai walls. I

5. A furnace tube adapted for use in the fixation of nitrogen by heating mixtures of alkali metal compounds and carbon in the presence of nitrogen, which comprises, an outer shell of oxidation resistant material, an inner shell ofmaterial which is not affected by said alkali metal compound, the walls of said shells being spaced, and a filler comprising finely divided iron and a reducing agent disposed between said walls.

6. furnace tube adapted for use in the fixation of nitrogenby heating mixtures of alkali metal compounds and carbon in the presence of nitrogen, which comprises, an outer shell of oxidation resistant material,

eliminates the disadvantage referred ade in the form, 5 arrangement and construction of the furadapted for use in the fixation of nitrogen by heating mixtures of an inner shell of material which is not afiected by said alkali metal compound, the walls of said shells being spaced, and a filler comprising finely divided iron and carbon disposed between said walls.

7. A furnace tube adapted for use in the fixation of nitrogen by heating mixtures of 10 fixation of nitrogen by heating mixtures of alkali metal compounds and carbon in the alkali metal compounds and carbon in the presence of nitrogen, which comprises, an presence of nitrogen, which comprises, an outer shell of nichrome, an inner shell of 3 outer shell of nichrome, an inner shell of ferrous metal, the walls of said shells being ferrous metal, the walls of said shells being spaced, and a filler comprising finely divided 15 spaced, and a filler comprising finely divided iron and carbon disposed between sald walls. iron disposed between said walls. In testimony whereof I aflix my signature.-

8. A furnace tube adapted for use in the FLOYD J. METZGER. 

